In the prior art, differentials which allow one axle to turn faster than the other are well-known. During a turn, the differential will permit one wheel to turn at a velocity different from the other. When the turn is completed, the axles rotate at the same velocity.
Presently in use are standard differentials, torque biasing differentials and overrunning clutches. In a standard differential, axle torques are equal and are limited by the wheel having the lesser tractive effort. Hence, if one wheel slips or spins, torque applied to the other wheel is reduced. The differential housing will thus rotate at the mean velocity of both wheels. A standard differential offers no resistance to steering. A torque biasing differential provides greater torque to the slower turning axle, which may be a fixed amount of torque transfer or an amount proportional to input torque magnitude. The torque transfer also occurs during turns so that the inner or slower turning wheel receives the greater torque. This produces a resistance to steering. In a torque biasing differential, the inner wheel, if it has poor traction, is forced to spin. An overrunning clutch can provide unlimited torque biasing during straight ahead operation, but transfers all torque to the inner wheel during a turn, while the outer wheel receives no torque. As a result, there is a high resistance to steering.